It's not easy (albiet my girl was a bit older) but I'm pretty sure parenting is a certain percentage of winging it, so to speak.

With my little girl, we talk about 'bubby' a lot. She also had her own 'bubby' (cabbage patch baby, so small enough for her to mother). Even now she changes her bubby's nappy, breastfeeds her bubby, changes her bubby.
When Nao was born, we had a gift from her for Munchkin. Just some crayons, it sort of eased the path.
But she used to kiss my belly and talk to bubby. We encouraged it a bit, but never forced her ifykwim? Everything was at her pace.

After she was born, as soon as Munchkin laid eyes on her, it was bubby bubby! (Not alot has changed). We just gently encouraged her to be a part of everything whilst also having her own special time with me and DH.

As for timing everything... A sling helped. Nao was in it almost every day at some point. But that's just bits of luck and perseverance.

I wish you the best of luck and I hope my experience can be a little bit of a help. (But everyones different )